This application is related to Japanese Patent Applications No. 2000-56974 filed on Mar. 2, 2000, and No. 2000-319313 filed on Oct. 19, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a vehicle air conditioner with a heating capacity control in a cooling water circuit having a heating heat exchanger for heating air. In the cooling water circuit, cooling water heated by an equipment that needs a temperature control circulates in the heating heat exchanger.
2. Description of Related Art
In a vehicle air conditioner, heating of a passenger compartment is performed using cooling water from an equipment that needs a temperature control, such as a water-cooled engine, as a heating source. When the heating of the passenger compartment is performed using cooling water of the water-cooled engine, a sufficient heating effect cannot be obtained when temperature of cooling water is low.
To overcome this problem, in a vehicle air conditioner described in JP-A-11-208250, an electrical heater is disposed in a cooling water circuit, and cooling water heated only by the electrical heater is supplied to a heater core in a closed water circuit without using heat from the engine until the temperature of cooling water in the engine becomes sufficiently high. On the other hand, when the temperature of cooling water in the engine is sufficiently high so that a sufficient heating effect can be obtained using cooling water from the engine, cooling water from the engine is supplied to the heater core, and the electrical heater is turned off. However, in this vehicle air conditioner, even when the temperature of cooling water in the engine increases and surplus heat is generated from the engine, when the temperature of cooling water in the engine is not increased to a temperature for obtaining the sufficient heating effect in the heater core, the heating of the passenger compartment is performed using the heat from the electrical heater in the closed water circuit. Accordingly, in this case, unnecessary heat discharged from the engine is not effectively used.
In view of the foregoing problems, it is an object of the present invention to provide a vehicle air conditioner which heats air using cooling water for a temperature control of an equipment as a heating source, in which a predetermined stable heating capacity of a passenger compartment can be obtained effectively using a surplus heat discharged from the equipment even when temperature of cooling water in the equipment is not sufficiently increased and a sufficient heating capacity is not obtained only using the heat of cooling water from the equipment.
According to the present invention, in an air conditioner for a vehicle having an equipment that needs a temperature control, a heating heat exchanger for heating air to be blown into a passenger compartment using cooling water as a heating source is disposed in a cooling water circuit, a supplementary heater for heating air is used for supplementing a heat quantity relative to the heating heat exchanger, a necessary heat quantity necessary for a heating of air blown into the passenger compartment is calculated based on a target air temperature, and a flow control unit controls a flow of cooling water in the cooling water circuit in such a manner that: cooling water from the equipment flows into the heating heat exchanger after temperature of the equipment increases to a predetermined temperature, and the flow of cooling water from the equipment to the heating heat exchanger is interrupted until the temperature of the equipment increases to the predetermined temperature. In the vehicle air conditioner, a heat quantity generated by the supplementary heater is used for supplementing an insufficient heat quantity when the heat quantity for heating air in the heating heat exchanger is smaller than the necessary heat quantity, after the temperature of the equipment increases to the predetermined temperature. Accordingly, when the temperature of the equipment increases the predetermined temperature, a surplus heat quantity unnecessary for the temperature control of the equipment is supplied to the heating heat exchanger. Therefore, even when the surplus heat quantity is a little, it can be effectively used for heating air. Further, when the surplus heat is insufficient for obtaining the necessary heat quantity in the heating heat exchanger, the insufficient heat quantity is supplemented by the supplementary heater. As a result, a predetermined heating capacity can be obtained.
On the other hand, until the temperature of the equipment increases to the predetermined temperature for a normal operation of the equipment, that is, when there is not the surplus heat discharged from the equipment, the flow of cooling water flowing into the heating heat exchanger is interrupted. Therefore, in this case, the temperature of the equipment can be rapidly increased, and it can prevent the temperature of the equipment from being lowered due to heat radiation from the heating heat exchanger. Even in this case, a heat-generating amount of the supplementary heater is controlled, so that the predetermined heating capacity can be obtained.